Rivet analyses

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Upsilon polarization at 7 TeV
  class CMS_2013_I1185414 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2013_I1185414);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(Beam(), "Beams");
      declare(UnstableParticles(), "UFS");
      // book profile hists for the moments
      // loop upsilon states
      for (unsigned int iups=0; iups<3; ++iups) {
        // rapidity intervals
        for (unsigned int iy=0; iy<2; ++iy) {
          // frame defns
          for (unsigned int iframe=0; iframe<3; ++iframe) {
            // 3 different moments
            for (unsigned int iobs=0; iobs<3; ++iobs) {
              const string name = "TMP/POL_"+toString(iups)+"_"+toString(iy)
                                 +"_"+toString(iframe)+"_"+toString(iobs);
              book(_p_Ups[iups][iy][iframe][iobs], name, refData(1,1,1));
            }
          }
        }
      }
    }

    void findDecayProducts(const Particle& mother, unsigned int& nstable,
                           Particles & mup, Particles & mum) {
      for (const Particle& p : mother.children()) {
        int id = p.pid();
        if (id == PID::MUON ) {
          ++nstable;
          mum.push_back(p);
        }
        else if (id == PID::ANTIMUON) {
          ++nstable;
          mup.push_back(p);
        }
        else if (id == PID::PI0 || id == PID::K0S || id == PID::K0L ) {
          ++nstable;
        }
        else if ( !p.children().empty() ) {
          findDecayProducts(p, nstable, mup, mum);
        }
        else {
          ++nstable;
        }
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // find the beams
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      // Final state of unstable particles to get particle spectra
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::pid==553 or Cuts::pid==100553 or Cuts::pid==200553)) {
        // check mu+mu- decay and find muons
        unsigned int nstable=0;
        Particles mup,mum;
        findDecayProducts(p,nstable,mup,mum);
        if (mup.size()!=1 || mum.size()!=1 || nstable!=2) continue;
        // pT and rapidity
        const double absrap = p.absrap();
        const double xp = p.perp();
        if (absrap>1.2 || xp<10. || xp>50.) continue;
        // type of upsilon
        unsigned int iups=p.pid()/100000;
        // rapidity interval
        unsigned int iy = absrap>0.6;
        // first the CS frame
        // first boost so upslion momentum =0 in z direction
        Vector3 beta = p.mom().betaVec();
        beta.setX(0.); beta.setY(0.);
        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(beta);
        FourMomentum pp = boost.transform(p.mom());
        // and then transverse so pT=0
        beta = pp.betaVec();
        LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(beta);
        // get all the momenta in this frame
        Vector3 muDirn = boost2.transform(boost.transform(mup[0].mom())).p3().unit();
        FourMomentum p1 = boost2.transform(boost.transform(beams. first.mom()));
        FourMomentum p2 = boost2.transform(boost.transform(beams.second.mom()));
        if (beams.first.mom().z()<0.) swap(p1,p2);
        if (p.rapidity()<0.) swap(p1,p2);
        Vector3 axisy = (p1.p3().cross(p2.p3())).unit();
        Vector3 axisz(0.,0.,1.);
        Vector3 axisx = axisy.cross(axisz);
        double cTheta = axisz.dot(muDirn);
        double cPhi   = axisx.dot(muDirn);
        // fill the moments
        _p_Ups[iups][iy][0][0]->fill(xp, 1.25*(3.*sqr(cTheta)-1.));
        _p_Ups[iups][iy][0][1]->fill(xp, 1.25*(1.-sqr(cTheta))*(2.*sqr(cPhi)-1.));
        _p_Ups[iups][iy][0][2]->fill(xp, 2.5 *cTheta*sqrt(1.-sqr(cTheta))*cPhi);
        // now for the HX frame
        beta = p.mom().betaVec();
        boost = LorentzTransform::mkFrameTransformFromBeta(beta);
        axisz = pp.p3().unit();
        axisx = axisy.cross(axisz);
        cTheta = axisz.dot(muDirn);
        cPhi   = axisx.dot(muDirn);
        // fill the moments
        _p_Ups[iups][iy][1][0]->fill(xp, 1.25*(3.*sqr(cTheta)-1.));
        _p_Ups[iups][iy][1][1]->fill(xp, 1.25*(1.-sqr(cTheta))*(2.*sqr(cPhi)-1.));
        _p_Ups[iups][iy][1][2]->fill(xp, 2.5 *cTheta*sqrt(1.-sqr(cTheta))*cPhi);
        // then PX
        axisz = (p1.p3().unit()+p2.p3().unit()).unit();
        axisx = axisy.cross(axisz);
        cTheta = axisz.dot(muDirn);
        cPhi   = axisx.dot(muDirn);
        // fill the moments
        _p_Ups[iups][iy][2][0]->fill(xp, 1.25*(3.*sqr(cTheta)-1.));
        _p_Ups[iups][iy][2][1]->fill(xp, 1.25*(1.-sqr(cTheta))*(2.*sqr(cPhi)-1.));
        _p_Ups[iups][iy][2][2]->fill(xp, 2.5 *cTheta*sqrt(1.-sqr(cTheta))*cPhi);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // Loop over states
      for (unsigned int iups=0; iups<3; ++iups) {
        // Loop over rapidity ranges
        for (unsigned int iy=0; iy<2; ++iy) {
          // Loop over frame definition
          for (unsigned int iframe=0; iframe<3; ++iframe) {
            // base no for the ihistos in rivet
            unsigned int ibase = 24*iups+iy+8*iframe;
            // book scatters
            Estimate1DPtr lTheta, lPhi, lThetaPhi, lTilde;
            book(lTheta, ibase+1, 1, 1);
            book(lPhi, ibase+3, 1, 1);
            book(lThetaPhi, ibase+5, 1, 1);
            book(lTilde   , ibase+7, 1, 1);
            // histos for the moments
            Profile1DPtr moment[3];
            for (unsigned int ix=0;ix<3;++ix) {
              moment[ix] = _p_Ups[iups][iy][iframe][ix];
            }
            // loop over bins
            for (unsigned int ibin=1; ibin<=moment[0]->bins().size(); ++ibin) {
              // extract moments and errors
              double val[3], err[3];
              // m1 = lTheta/(3+lTheta), m2 = lPhi/(3+lTheta), m3 = lThetaPhi/(3+lTheta)
              for (unsigned int ix=0; ix<3; ++ix) {
                bool has0 = moment[ix]->bin(ibin).numEntries()>0 && moment[ix]->bin(ibin).effNumEntries()>0;
                bool has1 = moment[ix]->bin(ibin).numEntries()>1 && moment[ix]->bin(ibin).effNumEntries()>1;
                val[ix] = has0? moment[ix]->bin(ibin).mean(2)   : 0.;
                err[ix] = has1? moment[ix]->bin(ibin).stdErr(2) : 0.;
              }
              // values of the lambdas and their errors
              double l1 = 3.*val[0]/(1.-val[0]);
              double l2 = (3.+l1)*val[1];
              // fill the scatters
              lTheta->bin(ibin).setVal(l1);
              lTheta->bin(ibin).setErr(3./sqr(1.-val[0])*err[0]);
              lPhi  ->bin(ibin).setVal(l2);
              lPhi  ->bin(ibin).setErr(3./sqr(1.-val[0])*sqrt(sqr(err[0]*val[1])+sqr(err[1]*(1.-val[0]))));
              lThetaPhi->bin(ibin).setVal((3.+l1)*val[2]);
              lThetaPhi->bin(ibin).setErr(3./sqr(1.-val[0])*sqrt(sqr(err[0]*val[1])+sqr(err[1]*(1.-val[0]))));
              lTilde   ->bin(ibin).setVal((l1+3.*l2)/(1.-l2));
              lTilde   ->bin(ibin).setErr( 3./sqr(1.-val[0]-3*val[1])*sqrt(sqr(err[0])+9.*sqr(err[1])));
            }
          }
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Profile1DPtr _p_Ups[3][2][3][3];
    /// @}


  };


  RIVET_DECLARE_PLUGIN(CMS_2013_I1185414);

}